Coated cutting insert and method for making the same

ABSTRACT

A coated cutting insert for removing material from a workpiece that includes a substrate is disclosed. A wear-resistant coating on the substrate that includes an alumina layer and a Zr- or Hf-carbonitride outer layer deposited on the alumina layer. The Zr- or Hf-carbonitride outer layer is subjected to a post-coat wet blasting treatment. The wet blasting changes the stress condition of the exposed alumina coating layer from an initial tensile stress condition to a compressive stress condition.

RELATED APPLICATION DATA

Pursuant to 35 U.S.C. §120, the present application is acontinuation-in-part application of U.S. patent application Ser. No.12/615,530, filed Nov. 10, 2008, the entirety of which is incorporatedherein by reference.

BACKGROUND OF THE INVENTION

The present invention pertains to a coated cutting insert useful for theremoval of material from a workpiece, e.g., chipforming machining of aworkpiece. More specifically, the present invention pertains to acutting insert useful for the removal of material from a workpiece,wherein the coated cutting insert comprises a substrate coated with amultilayer coating including a carbonitride of Zr or Hf and Al₂O₃. Thecoating scheme includes an exposed Zr or Hf coating layer exhibiting acompressive stress.

U.S. Pat. No. 6,224,968 to van den Berg et al. (assigned to KennametalInc.) discloses the use of a coating comprising first TiN layer, asecond carbonitride layer, a third Al₂O₃ layer and an outer Zr, Hf, V,Nb, Ta or Cr carbonitride layer on a hard metal, steel, cermet orceramic substrate.

U.S. Pat. No. 6,884,496 to Westphal et al. (assigned to Kennametal Inc.)discloses a method of increasing the compressive residual stress of orof reducing the tensile residual stress of a Zr or Hf carbonitridecoating layer through dry blasting the material with spray-formed hardmaterial metal granulate.

U.S. Pat. No. 6,350,510 to Konig et al. (assigned to Kennametal Inc.)discloses multiphase layer of Zr or Hf carbonitride having internalcompressive stresses. The compressive stress of the Zr or Hf layer isthe result of an uninterrupted CVD coating process between 900° C. and1100° C. followed by a heat treatment.

U.S. Patent Application Publication Nos. 2009/0004449 and 2009/0004440to Ban et al. (assigned to Kennametal Inc.) disclose wetblasting acutting insert with an outer wear resistant coating comprisingM(O_(x)C_(y)N_(z)) wherein M is selected from the group comprising oneor more of the following titanium, hafnium, zirconium, chromium,titanium-aluminum alloy, hafnium-aluminum alloy, zirconium-aluminumalloy, chromium-aluminum alloy, and their alloys, and x>0, y≧0, z≧0 andy+z>0.

SUMMARY OF THE INVENTION

A coated cutting insert for removing material from a workpiece thatincludes a substrate is provided. A wear-resistant coating on thesubstrate that includes an alumina (Al₂O₃) layer and a Zr- orHf-carbonitride outer layer deposited on the alumina layer. In someembodiments, the alumina layer is an α-alumina layer. The alumina layer,in some embodiments, is a κ-alumina layer. In some embodiments, thealumina layer comprises a mixture of α-alumina and x-alumina. Moreover,the Zr- or Hf-carbonitride outer layer is subjected to a post-coat wetblasting treatment. The wet blasting changes the stress condition of theZr- or Hf-carbonitride outer layer from an initial tensile or slightlycompressive stress condition to a more compressive stress condition.

An aspect of the invention is to provide a coated cutting insertcomprising a substrate and a multilayer coating scheme comprising anAl₂O₃ layer and an outer layer of ZrCN or HfCN on the Al₂O₃ layer,wherein the outer layer exhibits a blasted stress condition rangingbetween about −700 MPa and about −4.0 GPa as measured by XRD using thePsi tilt method and the (220) reflection of ZrCN. As described herein,the Al₂O₃ layer can be an α-Al₂O₃ layer, a κ-Al₂O₃ layer or a layercomprising a mixture of α-Al₂O₃ and κ-Al₂O₃.

In some embodiments, a coated cutting insert described herein comprisesa substrate and a multilayer coating scheme comprising an α-Al₂O₃ layerand an outer layer of ZrCN or HfCN on the α-Al₂O₃ layer, wherein theα-Al₂O₃ layer exhibits a blasted stress condition ranging from about 300MPa to about −1.0 GPa as measured by XRD using the Psi tilt method andthe (024) reflection of α-Al₂O₃. In some embodiments, a coating cuttinginsert described herein comprises a substrate and multilayer coatingscheme comprising a κ-Al₂O₃ layer and an outer layer of ZrCN of HfCN onthe κ-Al₂O₃ layer, wherein the κ-Al₂O₃ layer exhibits a blasted stresscondition ranging from about 200 MPa to about −1.3 GPa as measured byXRD using the Psi tilt method and the (122) reflection of κ-Al₂O₃.

A method of making a coated cutting insert, in some embodiments,comprises the steps of providing a substrate, coating the substrate witha multilayer wear-resistant coating including an Al₂O₃ layer and anouter Zr- or Hf-carbonitride outer layer on the Al₂O₃ layer, andsubjecting the outer layer to a wet blasting treatment. In someembodiments of methods described herein, the Al₂O₃ layer can be anα-Al₂O₃ layer, a κ-Al₂O₃ layer or a layer comprising a mixture ofα-Al₂O₃ and κ-Al₂O₃.

BRIEF DESCRIPTION OF THE DRAWINGS

The following is a brief description of the drawings that form a part ofthis patent application:

FIG. 1 is an isometric view of a specific embodiment of a coated cuttinginsert of the present invention wherein the coated cutting insert is ina post-blasted condition;

FIG. 2 is a partial cross-sectional view of the coated cutting insertillustrated in FIG. 1. The section illustrates a portion of the coatedcutting insert along section line A-B and near the surface of theinsert.

FIG. 3 is a photomicrograph of a section a coated cutting insertaccording to one embodiment of the present invention. The section showsa calotte scar exposing the substrate and coating layers on the flankface of the insert.

DETAILED DESCRIPTION

Referring to the drawings, FIG. 1 shows a coated cutting insert 10according to on5e embodiment of the present invention. Cutting insert 10is useful for the removal of material from a workpiece, e.g.,chipforming machining of a workpiece. The coated cutting insert 10 maypresent a cutting corner 11. FIG. 2 shows a cross-sectional view of thecutting of FIG. 1 along section line A-B and at cutting corner 11.

Referring still to FIG. 2, the cutting insert 10 has a substrate 12 witha multilayer coating the thereon. The substrate comprises a WC hardmetal, cermet, ceramic or steel. According to one embodiment of thepresent invention and beginning with the innermost coating adjacent thesubstrate and progressing outwardly, the layers of the multilayercoating include a TiN layer 13, a TiCN layer 14, an Al₂O₃ layer 15 andan outer coating 16. The TiCN layer 14 may be a moderate temperatureTiCN coating or a high temperature TiCN coating. In a certainembodiment, the Al₂O₃ layer 15 is a textured α-Al₂O₃ having apredominant (104) growth texture. In another embodiment, the Al₂O₃ layer15 is a κ-Al₂O₃ layer. Further, in some embodiments, the Al₂O₃ layer 15is a mixture of α-Al₂O₃ and κ-Al₂O₃. In some embodiments wherein theAl₂O₃ layer 15 is a mixture of α-Al₂O₃ and κ-Al₂O₃, the κ/α ratio isgreater than 1. In some embodiments, the κ/α ratio is greater than 10 orgreater than 100. The outer coating 16 comprises a Zr-based or Hf-basedcarbonitride, preferably ZrCN.

In a particular embodiment of the present invention, a bonding layer 18may be disposed between the Al₂O₃ layer 15 and an outer coating 16. Thebonding layer 18 can comprise M(O_(x)C_(y)N_(z)) wherein M is selectedfrom the group comprising one or more of the following titanium,hafnium, zirconium, chromium, titanium-aluminum alloy, hafnium-aluminumalloy, zirconium-aluminum alloy, chromium-aluminum alloy, and theiralloys, and x≧0, y≧0, z≧0 and y+z>0. When aluminum is present in the “M”component of the wear indicating layer, it is in combination withanother one or more of the other elements (i.e., titanium, hafnium,zirconium, chromium). Another embodiment of the present inventionprovides a (Ti_(1-b)Al_(b))(O_(x)C_(y)N_(z)) layer 17, wherein 0≦b<1,x≧0, y≧0, z≧0 and x+y+z>0. The (Ti_(1-b)Al_(b))(O_(x)C_(y)N_(z)) layer17, in some embodiments, is located between the TiCN layer 14 and theAl₂O₃ layer 15.

FIG. 3 is a photomicrograph of a section of a coated cutting insertaccording to one embodiment of the present invention. The section showsa calotte scar exposing the substrate and coating layers on the flankface of the insert. The photomicrograph shows a WC-Co substrate 20having a multilayer coating thereon. Beginning with the coating layeradjacent the substrate and progressing outwardly are the followinglayers, a TiN layer 22, an MT-TiCN layer 24, a TiOCN layer 26, anα-Al₂O₃ layer 28, and a ZrCN layer 30.

The Zr- or Hf-carbonitride outer layer coating may be applied by meansof CVD, whereby the gas phase, at a reaction temperature between 700° C.and 1100° C. and preferably at pressures between 5 kPA and 100 kPa,contains, in addition to H₂ and/or Ar and chlorides of theabove-mentioned metals, also carbon donors and nitrogen donors whichhave a C—N molecular group. This is preferably a cyanide group with atriple bond between the carbon and nitrogen, whose spacing at roomtemperature amounts to between 0.114 and 0.118 nm. Such compounds arehydrogen cyanide, cyanamide, cyanogen, cyanoacetylene or acetonitrile.Alternatively or in part, such gaseous compounds can also be used whichhave CN molecular groups with a single bond between the carbon and thenitrogen. Molecules with single CN bonds include methylamine andethylenediamine. The present invention includes within its frameworkappropriate substances containing the cyanide group; compounds of thiskind are in principle known in the state of the art. Other gaseous mediawhich are capable of forming cyano groups at the reaction temperaturecan be gated into the reaction vessel.

The thickness of the TiN 13 layer may be 0 to 2.0 μm, for example, 0.1to 0.5 μm. The thickness of the TiCN 14 layer may be 1.0 to 20.0 μm, forexample, 2.0 to 10 μm. The thickness of the Al₂O₃ layer 15 may be 1.0 to15.0 μm, for example 2.0 to 8.0 μm. In some embodiments wherein theAl₂O₃ layer is κ-Al₂O₃, the Al₂O₃ layer comprises a single κ-Al₂O₃ layeror multiple κ-Al₂O₃ layers. In some embodiments, for example, an Al₂O₃layer of a coating described herein comprises 2 to 30 κ-Al₂O₃ layers.Moreover, in some embodiments, an Al₂O₃ layer comprises alternatinglayers of κ-Al₂O₃ and α-Al₂O₃. In some embodiments,(Ti_(1-b)Al_(b))(O_(x)C_(y)N_(z)) layers are located between multipleκ-Al₂O₃ layers or alternating layers of κ-Al₂O₃ and α-Al₂O₃. Thethickness of the outer coating 16 may be 0.5 to 5.0 μm, for example 1.0to 3.0 μm. The post-coating wet blasting step removes outer coatinglayer 16 to a certain extent. The thickness of the outer coating 16 maybe 0.5 to 4.5 μm, for example 1.0 to 3.0 μm.

The multilayer coating is subjected to a post-coat wet blast treatment.The post-coating wet blasting step comprises pneumatically projectingalumina particles in a liquid (e.g., water) slurry to impinge allsurfaces of the pre-blasted coating scheme. The post-coating wetblasting step converts the tensile stress in the outer layer tocompressive stress or increases the compressive stress of the outerlayer. The post-coating wet blasting step also smoothens the surface ofthe outer coating layer 16. It is clear that the wet blasting step bothchanges the stress condition and smoothens the surface of the outercoating 16. The outer coating 16 (as-deposited) is in slight tension orcompression. In the case of slight tension, the post-coat wet blastingstep converts the tensile stress of the outer coating 16 to apost-blasted compressive stress level. In the case of slightcompression, the post-coating wet blasting step further increases thecompressive stress of the outer coating layer 16.

The post-coating wet blasting step also leads to smoothening of theouter coating 16. In one alternative, the exposed alumina coating layerexhibits a surface roughness R_(a) of between about 0.2 μm and about 0.5μm using a WYKO measurement technique. In another alternative, theexposed alumina coating layer exhibits a surface roughness R_(a) ofbetween about 0.2 μm and about 0.4 μm using a WYKO measurementtechnique. In still another alternative, the exposed alumina coatinglayer exhibits a surface roughness R_(a) of between about 0.3 μm andabout 0.4 μm using a WYKO measurement technique. In another alternative,the exposed alumina layer exhibits a surface roughness R_(a) less than0.2 μm using a WYKO measurement. In regard to the WYKO technique, asampling area of 0.3 mm by 0.2 mm was chosen in WYKO measurement underthe Vertical Scanning Interferometry mode.

In one alternative of the wear-resistant coating scheme, the outercoating exhibits a pre-blasted (or as-deposited) stress condition equalto between about 100 MPa tensile stress to about −400 MPa compressivestress. As used herein, when referring to stress conditions of a coatinga positive number indicates a tensile condition and a negative numberindicates a compressive condition. After completion of the wet blasting,the outer coating layer 16 has a compressive stress condition of between−700 MPa to about −4.0 GPa. In another alternative, the outer coating 16exhibit a stress condition of between −2.0 GPa to about −4.0 GPa aftercompletion of the wet blasting.

In another alternative of the wear-resistant coating scheme, the Al₂O₃layer 15 exhibits a pre-blasted (or as-deposited) stress conditionranging from about 200 MPa tensile stress to about 800 MPa tensilestress. After completion of the wet blasting, the Al₂O₃ layer 15 has atensile/compressive stress condition of between 300 MPa to about −1.0GPa. In some embodiments, the Al₂O₃ layer has a tensile/compressivestress condition ranging from about 200 MPa to about −1.3 GPa aftercompletion of wet blasting. The Al₂O₃ layer, in some embodiments, has acompressive stress condition ranging from about −200 MPa to about −1.5GPa after completion of wet blasting. In some embodiments, the Al₂O₃layer has a compressive stress condition ranging from about −500 MPa toabout −1.0 GPa after completion of wet blasting. As described furtherherein, the Al₂O₃ layer having a tensile or compressive stress conditionrecited herein can be an α-Al₂O₃ layer, a κ-Al₂O₃ layer or a layercomprising a mixture of α-Al₂O₃ and κ-Al₂O₃.

In reference to the measurement technique for the stress of a ZrCN outercoating, the technique is x-ray diffraction (XRD) technique. The XRDstress measurement is based upon the Psi tilt method and the reflection(220) of the ZrCN coating layer was chosen for measurement. Psi tilts of0 degrees, 28.9 degrees, 43.1 degrees, 56.8, an 75 degrees were selectedfor the measurement of the residual stress levels. Positive and negativePsi tilts were chosen to supply the data required to determine possibleshear stresses. Additionally, three Phi rotation angles were selected (0degrees, 45 degrees, and 90 degrees) to provide the data required todetermine the biaxial stress state of the material.

Biaxial stress calculations were completed using the following equation:

$\frac{d_{\phi \; \psi} - d_{0}}{d_{0}} = {{S_{1}\left( {\sigma_{1} + \sigma_{2}} \right)} + {\frac{1}{2}S_{2}\sigma_{\phi}\sin^{2}\psi}}$

where:

-   -   S₁ and ½ S₂ are the x-ray elastic constants    -   d_(φψ) measured peak d-spacing for the Psi tilt and Phi rotation    -   d₀ stress free peak d-spacing for diffracted reflection    -   σ₁ and σ₂ are the primary stresses

σ_(φ)=σ₁ cos² φ+σ₂ sin² φ

Young's Modulus (E) is taken to be 434 GPa, Poisson's Ratio (ν) is takento be 0.2, and x-ray elastic constants (S₁ and S₂) are taken to be−0.46×10⁶ mm²/N and 2.76×10⁶ mm²/N respectively for calculation ofstress in ZrCN coating. Similar measurements may be done for an HfCNcoating.

In reference to the measurement technique for the stress of the Al₂O₃layer, the technique is essentially the same as above with the followingexceptions. In embodiments wherein the Al₂O₃ layer is an α-Al₂O₃ layer,the reflection (024) of the α-Al₂O₃ layer was chosen for measurement.Young's Modulus (E) is taken to be 401 GPa, Poisson's Ratio (ν) is takento be 0.22, and x-ray elastic constants (S₁ and S₂) are taken to be−0.53×10⁶ mm²/N and 2.94×10⁶ mm²/N respectively for calculation ofstress in α-Al₂O₃ coating. Moreover, in embodiments wherein the Al₂O₃layer is a κ-Al₂O₃ layer, the (122) reflection of the κ-Al₂O₃ layer waschosen for measurement. Young's Modulus (E) for the κ-Al₂O₃ layer istaken to be 408 GPa, Poisson's Ratio (ν) is taken to be 0.22, and x-rayelastic constants (S₁ and S₂) are taken to be −0.56×10⁶ mm²/N and3.01×10⁶ mm²/N respectively for calculation of stress in κ-Al₂O₃coating.

The wet blasting is accomplished using a slurry comprising aluminaparticulates and water. The slurry of alumina particulates and water ispneumatically projected at the surface to impinge the surface of thesubstrate. The fundamental parameters of the alumina-water slurry aregrit (i.e., alumina particles) concentration in volume percent, andalumina particle size in micrometers (μm). In one alternative, theslurry comprises between about 5 volume percent and about 35 volumepercent alumina particulates with the balance water. In anotheralternative, the slurry comprises between about 8 volume percent andabout 25 volume percent alumina particulates with the balance water. Forthe particle size, in one alternative, the alumina particles can rangein size between about 20 μm and about 100 μm. In another alternative,the alumina particles can range in size between about 35 μm and about 75μm.

The operating parameters for the wet blasting step are pressure, angleof impingement, and duration. In this application, the angle ofimpingement is about ninety degrees, i.e., the particles impinge thesurface at a ninety degree angle. In one alternative, the pressureranges between about 35 pounds per square inch (psi) and about 55 psi.In another alternative, the pressure ranges between about 40 pounds persquare inch (psi) and about 50 psi. The duration of the wet blastingvaries with the specific wet blasting operation wherein the goal is toachieve optimum stress levels in the outer coating and Al₂O₃ layer.Exemplary durations comprise between about 6 seconds and about 45seconds. One range of duration is between about 9 seconds and about 30seconds. Still another range of duration is between about 12 seconds andabout 21 seconds.

In reference to a method of making a coated cutting insert, the basicsteps comprise the following steps. The first step comprises providing asubstrate wherein the substrate is selected from the group consisting ofhard metals, cermets or ceramics. Second, the substrate is coated with amultilayer wear-resistant coating including an Al₂O₃ layer and an outerZr- or Hf-carbonitride outer layer on the Al₂O₃ layer. As describedherein, the Al₂O₃ layer can be an α-Al₂O₃ layer, a κ-Al₂O₃ layer or alayer comprising a mixture of α-Al₂O₃ and κ-Al₂O₃. Third, the coating issubjected to a wet blasting treatment.

Specific examples of the inventive coated cutting insert and thecomparative testing thereof are set forth below. One comparative testmeasured the tool life in minutes of an inventive coated cutting insertagainst the tool life in minutes of two other prior art cutting insert.

Table 1 sets out the basic process parameters used to deposit thealumina-containing base coating region and the zirconium-containingouter coating region for the specific examples, both of the prior artand of the inventive ceramic cutting insert. In this regard, the processof parameters in Table 1 represents the steps used to apply a coatingscheme to the surface of the cemented carbide substrate.

TABLE 1 Process Parameters for Invented coating process TemperaturePressure Total Time Materials (° C.) (mbar) (minutes) Gases Utilized TiN 905 160  60 H₂, N₂, TiCl₄ HCl TiCN  880 70-90  240 TiCl₄, H₂, N₂,CH₃CN, Ar (Ti_(1−b)Al_(b))(O_(x)C_(y)N_(z)) 1000 75-600 70 H₂, N₂, CH₄,TiCl₄, CO, AlCl₃, α-Al₂O₃ 1000 75 300 H₂, AlCl₃, CO₂, HCl, H₂S ZrCN960-1000 80 240 ZrCl₃, H₂, CH₃CN, ArThe above steps occur in sequence beginning with the TiN step throughthe step to apply the ZrCN.

In reference to the above steps in Table 1, control of the Al₂O₃ toensure α-phase results, in some embodiments, is important to theintegrity of the outer coating. Poor adhesion between ZrCN and otheralumina phases can lead to flaking of the outer layer during wetblasting or metalcutting. However, coated cutting inserts of the presentinvention comprising a κ-Al₂O₃ layer can demonstrate adhesion betweenZrCN and the κ-Al₂O₃ suitable for wet blasting and/or metal cuttingapplications, thereby offering an alternative to α-Al₂O₃ embodiments.Therefore, in reference to the above steps in Table I, the deposition ofthe Al₂O₃, in some embodiments, is controlled to ensure the κ-phaseresults.

In a first example, prior art cutting inserts used in the comparativetesting comprised a coating scheme similar to the present invention withthe exception being the prior art inserts utilize a TiCN/TiN outercoating layer. The cutting inserts of the present invention of thisfirst example displayed the coating structure in Table I wherein anα-Al₂O₃ layer is used in conjunction with the ZrCN outer layer. Both theprior art coated cutting inserts and the inventive coated ceramiccutting insert were ANSI Standard CNMA432 cutting inserts.

TABLE 2 Post-Coating Blasting Parameters Parameter DescriptionComposition of the alumina In the range of 5%-35% by volumeparticle-water slurry Size of the alumina particles In the range of 20μm-100 μm Pressure during the In the range of 35 psi-55 psi impingementprocess Duration of the Impingement In the range of 6 seconds to 45seconds

For the comparative testing measuring tool life, the parameters were asfollows: workpiece material: 80-55-06 ductile iron; speed equal to 656surface feet per minute (sfm) (200 surface meters per minute); a feedrate equal to 0.004 inch (0.1 millimeters) per revolution (ipr); a depthof cut (doc) equal to 0.08 inch (2.03 millimeters); a lead angle equalto −5 degree with coolant. The failure criteria were: UNF equal to 0.012inches (0.3 millimeters) maximum; nose wear (NW) equal to 0.012 inches(0.3 millimeters); depth of cut notching (DOCN) equal to 0.012 inches(0.3 millimeters); CR equal to 0.004 inches (0.1 millimeters); and TWequal to 0.012 inches (0.3 millimeters).

In the comparative testing, samples, i.e., three each of the prior artcoated cutting inserts and three inventive coated cutting inserts, wererun. The results of the comparative testing are set forth in Table 3below.

TABLE 3 Tool Life Results from Comparative Testing Tool Life(Minutes)/Failure Mode Prior Art - 1A 10.3/NW  Prior Art - 2A 9.6/NWPrior Art - 3A 7.3/NW Invention - 1 14.0/NW  Invention - 2 9.9/NWInvention - 3 11.9/NW These cutting test results show approximately 30% improvement in thelife time (tool life) of the inventive cutting inserts in the wearresistance as compared to the wear resistance of the prior art cuttinginserts.

A second comparative measuring notching resistance was also performed. Awet turning cycle was used with the following parameters: workpiecematerials: 316 Ti stainless steel; speed equal to 656 surface feet perminute (sfm) (200 surface meters per minute); a feed rate equal to 0.01inch (0.25 millimeters) per revolution, and a depth of cut equal to 0.08inch (2 millimeters); and a lead angle equal to −5 degrees. The priorart is a commercial carbide cutting tool coated kappa Al₂O₃ with ZrCNtop layer treated with dry blasting. The cutting insert of the presentinvention in this example displayed the coating architecture of Table I.Both the prior art coated cutting inserts and the inventive coatedcutting insert have the style of the ANSI Standard CNMG432RP. Table 4below sets forth results of a comparison of the tool life determined bydepth of cut notching for the prior art coated cutting insert and theinventive coated cutting insert. The failure criterion is: depth of cutnotching (DOCN) equal to 0.012 inches (0.3 millimeters).

TABLE 4 Comparison of Prior Art Cutting Inserts and Inventive CuttingInserts Tool life by DOCN (in minutes) Prior Art Insert 10.7 InventiveInsert 12.7The inventive cutting inserts exhibited 20% improvement in depth ofnotch resistance in machining 316 Ti stainless steel.

The patents and other documents identified herein are herebyincorporated in their entirety by reference herein. Other embodiments ofthe invention will be apparent to those skilled in the art from aconsideration of the specification or a practice of the inventiondisclosed herein. There is the intention that the specification andexamples are illustrative only and are not intended to be limiting onthe scope of the invention. The following claims indicate the true scopeand spirit of the invention.

1. A coated cutting insert comprising: a substrate; and a multilayercoating scheme comprising: an Al₂O₃ layer; and an outer layer of ZrCN orHfCN on the Al₂O₃ layer, wherein the outer layer exhibits a blastedstress condition ranging between about −700 MPa to about −4.0 GPa asmeasured by XRD using the Psi tilt method and the (220) reflection ofZrCN or HfCN.
 2. The coated cutting insert of claim 1 wherein theblasted stress condition ranges between about −2.0 GPa and about −4.0GPa.
 3. The coated cutting insert of claim 1 wherein the multilayercoating scheme further comprises an innermost TiN and a TiCN layer onthe TiN layer, wherein the Al₂O₃ layer is on the TiCN layer.
 4. Thecoated cutting insert of claim 1, wherein the Al₂O₃ layer is a κ-Al₂O₃layer.
 5. The coated cutting insert of claim 1, wherein the Al₂O₃ layeris an α-Al₂O₃ layer.
 6. The coated cutting insert of claim 1, whereinthe Al₂O₃ layer comprises a mixture of α-Al₂O₃ and κ-Al₂O₃
 7. The coatedcutting insert of claim 1 further comprising a bonding layer between theAl₂O₃ layer and an outer layer, the bonding layer comprisingM(O_(x)C_(y)N_(z)) wherein M is selected from the group comprising oneor more of the following titanium, hafnium, zirconium, chromium,titanium-aluminum alloy, hafnium-aluminum alloy, zirconium-aluminumalloy, chromium-aluminum alloy, and their alloys, and x≧0, y≧0, z≧0 andy+z>0, and whereby when M is aluminum, then at least one of titanium,hafnium, zirconium or chromium is also present.
 8. The coated cuttinginsert of claim 3 further comprising a (Ti_(1-b)Al_(b))(O_(x)C_(y)N_(z))layer between the TiCN layer and the Al₂O₃ layer, wherein 0≦b<1, x≧0,y≧0, z≧0 and x+y+z>0
 9. The coated cutting insert of claim 1 wherein thesubstrate comprises a hard metal, a cermet or a ceramic.
 10. The coatedcutting insert of claim 1 wherein the outer layer has a thickness of 0.5μm to 4.5 μm and the Al₂O₃ layer has a thickness of 1.0 μm to 15.0 μm.11. The coated cutting insert of claim 10, wherein the Al₂O₃ layercomprises multiple κ-Al₂O₃ layers.
 12. The coated cutting insert ofclaim 10, wherein the Al₂O₃ layer comprises alternating layers ofκ-Al₂O₃ and α-Al₂O₃.
 13. A coated cutting insert comprising: asubstrate; and a multilayer coating scheme comprising: a κ-Al₂O₃ layer;and an outer layer of ZrCN or HfCN on the κ-Al₂O₃ layer, wherein theκ-Al₂O₃ layer exhibits a blasted stress condition ranging between about200 MPa to about −1.3 GPa as measured by XRD using the Psi tilt methodand the (122) reflection of κ-Al₂O₃.
 14. The coated cutting insert ofclaim 13 wherein the multilayer coating scheme further comprises aninnermost TiN and a TiCN layer on the TiN layer, wherein the κ-Al₂O₃layer is on the TiCN layer.
 15. The coated cutting insert of claim 13further comprising a bonding layer between the κ-Al₂O₃ layer and anouter layer, the bonding layer comprising M(O_(x)C_(y)N_(z)) wherein Mis selected from the group comprising one or more of the followingtitanium, hafnium, zirconium, chromium, titanium-aluminum alloy,hafnium-aluminum alloy, zirconium-aluminum alloy, chromium-aluminumalloy, and their alloys, and x≧0, y≧0, z≧0 and y+z>0, and whereby when Mis aluminum, then at least one of titanium, hafnium, zirconium orchromium is also present.
 16. The coated cutting insert of claim 15further comprising a (Ti_(1-b)Al_(b))(O_(x)C_(y)N_(z)) layer between theTiCN layer and the κ-Al₂O₃ layer, wherein 0≦b<1, x≧0, y≧0, z≧0 andx+y+z>0
 17. The coated cutting insert of claim 13 wherein the substratecomprises a hard metal, a cermet or a ceramic.
 18. The coated cuttinginsert of claim 13 wherein the κ-Al₂O₃ layer comprises multiple κ-Al₂O₃layers.
 19. The coated cutting insert of claim 13, wherein the κ-Al₂O₃layer further comprises alternating layers of κ-Al₂O₃ and α-Al₂O₃. 20.The coated cutting insert of claim 13 wherein the outer layer has athickness of 0.5 μm to 4.5 μm and the κ-Al₂O₃ layer has a thickness of1.0 κm to 15.0 μm.
 21. The coated cutting insert of claim 13, whereinκ-Al₂O₃ layer exhibits a blasted stress condition ranging between about−200 MPa to about −1.5 GPa
 22. A method of making a coated cuttinginsert comprising the steps of: providing a substrate; coating thesubstrate with a multilayer wear-resistant coating including an Al₂O₃layer and an outer Zr- or Hf-carbonitride outer layer on the Al₂O₃layer; and subjecting the outer layer to a wet blasting treatment. 23.The method making a coated cutting insert according to claim 22 whereinthe wet blasting treatment utilizes a slurry comprising aluminaparticles and water, wherein the alumina comprises 5% to 35% by volumeof the slurry.
 24. The method making a coated cutting insert accordingto claim 22 wherein the alumina particles are 20 μm-100 μm.
 25. Themethod making a coated cutting insert according to claim 22 wherein theslurry is blasted at a pressure of 35 psi to 55 psi and the wet blastingcontinues for six seconds to forty-five seconds.
 26. The method of claim22, wherein the Al₂O₃ layer is a κ-Al₂O₃ layer.
 27. The method of claim22, wherein the Al₂O₃ layer is an α-Al₂O₃ layer.
 28. The method of claim22, wherein the Al₂O₃ layer comprises a mixture of α-Al₂O₃ and κ-Al₂O₃.